Upscale

Enlarges the finished image with a dedicated upscaling model.

Costs time Costs kudos Makes the same picture larger; the composition is already decided

It runs after generation, on the picture the model produced, so it changes nothing about the composition and cannot rescue a bad one. The plain and anime variants of RealESRGAN suit photographic and drawn work respectively. At most one upscaler runs, so picking a second replaces the first. It is a different tool from the hires pass, which enlarges mid-generation and repaints as it goes.
Finishing · Interactive explorer Upscale
The same picture rendered at RealESRGAN_x4plusUpscale RealESRGAN_x4plus 2048 × 2048

The general-purpose choice, four times the size. Detail that was never rendered is invented plausibly rather than recovered, which is what every upscaler on this strip is doing.

Fetching the example images.

Where the difference is

One setting against another, close up The same patch cut from both pictures, drawn one picture pixel to one screen pixel.
Compare against
A close-up patch of RealESRGAN_x4plus
RealESRGAN_x4plus
A close-up patch of 4x_AnimeSharp
4x_AnimeSharp

RealESRGAN_x4plus · 532 × 532 4x_AnimeSharp · 532 × 532

The same picture before and after, close up The same patch cut from both pictures, drawn one picture pixel to one screen pixel.
Compare against
A close-up patch of Source
SourceEnlarged 4x to match
A close-up patch of 4x AnimeSharp
4x AnimeSharp

Source · 133 × 133 4x AnimeSharp · 532 × 532